Privacy

The summary

This site sets no cookies. It runs no analytics. It loads no fonts, scripts, images or stylesheets from any other domain. It has no accounts, no newsletter and no comment system. It does not use local storage or session storage.

There are three small pieces of JavaScript, all served from this domain. The step solver is a calculator that makes no network requests at any point. The search page fetches one index file from this domain and filters it locally, so no query is transmitted. The contact form posts your message when you press send, and only then.

That last one is the single exception to everything above, and it has its own section below.

You do not have to take our word for any of this, and the section on verification below explains how to check it in about a minute.

Why there is no cookie banner

Because there are no cookies. Consent requirements under the ePrivacy Directive and similar regimes apply to storing or accessing information on your device that is not strictly necessary for a service you requested. Nothing here stores anything on your device beyond the ordinary browser cache for the pages themselves.

A cookie banner on a site with no cookies would be theatre, and the reason so many exist is that a site with three trackers finds it cheaper to install a consent tool than to remove the trackers.

What the hosting provider sees

This is the part most privacy policies obscure, so here it is plainly.

Static files have to be served by a machine, and that machine receives a request from your browser. The request necessarily contains your IP address, because that is how the response gets back to you. It also contains whatever your browser sends by default: the user agent string, the requested path, the referring page if you arrived through a link, and your language preference headers.

Hosting providers typically write these into an access log, retained for a period, used for operational purposes such as diagnosing failures and detecting abuse. We do not configure this, do not query it, and do not connect it to anything.

An IP address is personal data under the GDPR. The lawful basis for the host's processing is legitimate interest in operating and securing the service, which is the standard basis for server logs and is narrow: the logs cannot lawfully be used to build a profile of you, and they are not.

If you would rather not share your address with the host at all, a VPN or Tor works here as it does anywhere, and nothing on this site will break as a result.

The step solver

Everything you type into the calculator is processed by JavaScript running in your browser. The expression is tokenised, converted to reverse Polish notation and evaluated locally. The result is written into the page.

No request is made. Nothing is stored. Nothing is logged. Reloading the page discards everything.

This is not a policy commitment that could quietly change. It is a property of the code, which is served from this domain at /assets/solver.js, is a few hundred lines, and contains no fetch, no XMLHttpRequest, no WebSocket and no storage call. You can read it.

The contact form

This is the one place on the site where something you type is transmitted, and it happens only when you press send.

The form posts to FormSubmit, a third-party relay that forwards the message to our inbox. It exists because this site is static files with no server of its own, and a form has to post somewhere. What is sent is exactly what the form shows: your name, your email address, the topic you picked, the article field if you filled it, and your message. FormSubmit also sees the network metadata that any recipient of an HTTP request sees, including your IP address, and it applies its own spam filtering to decide whether to forward.

No script from that service is loaded on the page. Nothing is set in your browser by it. Nothing is recorded while you type. Open the network tab and type into the form for as long as you like: there is one request, when you submit, and nothing before it.

FormSubmit is a separate company with its own privacy policy and its own retention practices, which we do not control. If you would rather not involve a relay, do not use the form. Nothing is transmitted unless you press send, and the rest of the site works without it.

The lawful basis for handling what you send is legitimate interest in responding to correspondence. Your address is used to reply to you and nothing else. It is never added to a list, because there is no list.

How to verify this yourself

Open your browser's developer tools before loading a page here. In Firefox or Chrome that is F12, or right-click and choose Inspect.

Go to the Network tab and reload. You will see requests for the HTML document, one stylesheet, and on the solver, search and contact pages one JavaScript file each. Every one is served from this domain. There are no requests to any analytics endpoint, font provider, CDN or tag manager, because there is nothing here to make them.

Go to the Application or Storage tab and look at Cookies, Local Storage and Session Storage. All empty.

Now use the solver. Watch the Network tab while you evaluate an expression. Nothing appears.

Do the same on the search page. One request for the index when the page loads, then nothing however much you type. On the contact page, nothing appears until you press send.

This check takes under a minute and it is worth doing on any site that makes claims like these, including this one. A privacy policy is a promise. The network tab is evidence.

Correspondence

If you write to us, we have whatever you put in the form, including the address you gave us to reply to. There is no way to answer you otherwise.

Messages are read by the editors and kept while the matter is open. Correspondence about a correction is retained alongside the article's revision history, because a correction note needs to be traceable to what prompted it. Other correspondence is deleted when it is no longer needed, generally within a year.

Your address is never added to any list, shared with anyone, or used for anything other than replying to you. There is no list to add it to.

If you are credited in a correction note, only the name you ask to be credited under appears, never your address. If you prefer not to be credited, say so and you will not be.

External links

Articles link to papers, repositories and other sites. Following a link takes you to a service with its own practices, which are frequently very different from these.

The links are plain anchors to the destination. There is no redirect through a tracking service, no link decoration, and no click measurement, because there is nothing here to measure with.

Your rights

Under the GDPR and comparable regimes you have rights to access, rectify, erase and port your personal data, to object to processing, and to complain to a supervisory authority.

In practice, the only personal data we hold is correspondence you sent us through the form. If you want a copy of it, or want it deleted, ask through the contact form and it will be handled within thirty days.

Server logs held by the hosting provider are subject to that provider's own retention schedule. We can pass on a request but we do not administer those systems.

Children

The site is not directed at children and the material is written for a general adult audience with secondary-school mathematics. Nothing is collected from anyone who does not deliberately send a message, and we do not knowingly hold correspondence from a child. If you believe we do, write and it will be deleted.

Data transfers

Static files are served from a content delivery network with points of presence in multiple countries, so the request that returns a page to you is handled by whichever location is nearest. Since no personal data is collected in the process beyond the transient request handling described above, there is no cross-border transfer of a dataset to disclose.

Security

The site is served over HTTPS. There is no login, no session, no user data at rest, and no server-side code, which removes most of the categories of vulnerability that affect web applications. The remaining risk surface is the hosting account itself and the DNS.

If you find a security issue, report it through the contact form. We will confirm receipt and tell you what we did.

Changes

Material changes to this notice will be described on this page for at least sixty days, with the date updated at the top.

The specific change that would matter is adding analytics of any kind. Should that ever happen, it would be stated here in plain terms, at the top, before it went live, and it would say exactly what is collected and by whom. The current intention is that it will not happen.